Health comprises resources necessary for resisting illness, adapting to demands and disease, and flourishing. For children, health is the foundation for engaging in increasingly challenging activities that stimulate physical, cognitive, and social development. Currently, we lack a common set of patient-reported outcome measures that span disease categories and age ranges for pediatric clinical research and practice. Instruments developed for adults are unlikely to capture the realities of childhood that result from developmental change, and they typically are not suitable in terms of reading comprehension and respondent burden. The goal of the proposed project is to develop novel measures of children's perceived health-child and parent respondent editions-that are based in a comprehensive, consensus-derived, developmentally informed, child-sensitive model of health. Specifically, our aims are to: (1) conceptualize and integrate within the existing PROMIS framework the novel pediatric perceived health constructs of physical activity, physical comfort/symptoms, experience of stress, subjective well-being, family belonging, and school belonging; (2) develop pediatric item pools for these health constructs; (3) calibrate, validate, and developmentally equate the item pools among 5,000 parent/child dyads; and, (4) perform a clinical validation study of PROMIS item banks among 400 children with inflammatory bowel disease (IBD). We will use literature reviews, secondary data analyses, focus groups, and an international/cross-cultural consensus development process to expand the PROMIS conceptual framework to ensure it is sensitive to the unique characteristics of children. Data will be collected at two of the nation's largest pediatric integrated delivery systems and several school systems. A key innovation is our focus on children's development, a sensitivity that will imbue the conceptualization of child health, qualitative approaches to item pool development, and statistical methods for analyzing developmental change. Our team of child health experts and pediatric perceived health instrument developers has arguably contributed more to the conceptualization and measurement of health and disease in childhood and adolescence than any other group in the world.